Author Topic: carpy's frame kit (Read 10795 times)

Ricky_Racer · « **Reply #25 on:** June 21, 2010, 07:43:54 PM »

Yep. And they also give us a nice place to support a race tank.

And how about a pic of the old APE kit? I've never seen one. Thanks! RR

Terry in Australia · « **Reply #26 on:** June 21, 2010, 07:48:15 PM »

I can't understand why Carpy didn't weld on a couple of tabs so that you could tie the bottom rails to the top rail, the CB750 is a heavy bike, and the mild steel frame needs all the bracing that Honda engineered into it, and then some.

I've posted pics in an old thread somewhere of the "Big Benly" bike that Cycle World built in 1999, and the amount of extra bracing required (particularly in that area) to make the bike handle at high speed was substantial, so even for a bike ridden "carefully" (if there's such a way) I certainly wouldn't remove any factory bracing, particularly with the spindly 35mm OEM forks and crap shocks.

Modern tires with their stickier compounds will exacerbate the problem, making the 30+ year old frame flex more than it ever has before, and could well crack the frame, or even spit you off. If I were you, I'd weld a couple of tabs onto the lower tubes and bolt them on to the remains of the factory triangular brace, to return some of the factory rigidity. just my two cents, and I'm not trying to rain on your parade mate, I just don't understand why Carpy thought it was unnecessary, considering that his bikes are (loosely) termed Cafe Racers, when that's obviously not a mod any self respecting racer would consider......... Cheers, Terry.

bikerbart · « **Reply #27 on:** June 21, 2010, 07:54:44 PM »

that is precicely why I left the tabs.Sheeesh,why do you guy's have to harsh my mellow man?

Terry in Australia · « **Reply #28 on:** June 21, 2010, 08:01:00 PM »

Sorry mate, I'd just rather see you safe, than sorry.

axehole54 · « **Reply #29 on:** June 21, 2010, 08:23:33 PM »

Quote from: Terry in Australia on June 21, 2010, 07:48:15 PM

I can't understand why Carpy didn't weld on a couple of tabs so that you could tie the bottom rails to the top rail, the CB750 is a heavy bike, and the mild steel frame needs all the bracing that Honda engineered into it, and then some.

I've posted pics in an old thread somewhere of the "Big Benly" bike that Cycle World built in 1999, and the amount of extra bracing required (particularly in that area) to make the bike handle at high speed was substantial, so even for a bike ridden "carefully" (if there's such a way) I certainly wouldn't remove any factory bracing, particularly with the spindly 35mm OEM forks and crap shocks.

Modern tires with their stickier compounds will exacerbate the problem, making the 30+ year old frame flex more than it ever has before, and could well crack the frame, or even spit you off. If I were you, I'd weld a couple of tabs onto the lower tubes and bolt them on to the remains of the factory triangular brace, to return some of the factory rigidity. just my two cents, and I'm not trying to rain on your parade mate, I just don't understand why Carpy thought it was unnecessary, considering that his bikes are (loosely) termed Cafe Racers, when that's obviously not a mod any self respecting racer would consider......... Cheers, Terry.

Might that be why my bike feels squirrly when i start leaning into the corners especially on the down slopes? I had suspected it as i have the modern stickies and they bite hard

MCRider · « **Reply #30 on:** June 21, 2010, 08:37:54 PM »

Quote from: Ricky_Racer on June 21, 2010, 07:43:54 PM

Yep. And they also give us a nice place to support a race tank.

And how about a pic of the old APE kit? I've never seen one. Thanks! RR

here tis, with the original APE decals still affixed, never installed (I have 2), its the 2 tubes and 4 sliding joints at the top.

Ricky_Racer · « **Reply #31 on:** June 21, 2010, 10:26:30 PM »

Aha! Thanks, Bro!

RR

nippon · « **Reply #32 on:** June 22, 2010, 01:47:06 AM »

I think a one piece frame tube is stonger than a 8 bolt connection, especially with the soft stock CB750 frame. Then, i do not like to see frames in good shape cut down.
I do not like to work on a engine with limited space, caused by the frame down tubes and front triangle.
Normally, i work one time on a head, then i put it in the frame. In case (If i have to) of retightening the cylinder nuts
after a rebuilt, i pull the engine wsithin one hour and back within one hour, so this is no big deal.
Anyway, when i pull the engine, then normally i have to open the cases for replacing primary chains or what ever. Then the kit will not help.
I just think, .....limited advantages for a good reason to cut down a stock frame.
What is the installation time for the kit? The same as pulling an engine out of the frame and back?
Probably it's good for racers who have to fix a problem between races with limited time.
In relation between my riding time and the time i have to work on the engine, I prefer a stiffer frame w/o such a kit during my rides.
....just my opinion.

nippon

Swoop · « **Reply #33 on:** June 22, 2010, 04:14:48 AM »

Quote from: MCRider on June 21, 2010, 06:49:38 PM

How about a link to the kit. I've been thru Carpy's site and don't see it.

$65

http://www.cb750cafe.com/parts.php?id=119

Steve

HedNut · « **Reply #34 on:** June 22, 2010, 04:58:22 AM »

Neat! I'm suprized it's so cheap!...and definately effective at making the upper end accessable.
But I still feel safer on the excellent engineering and gentle love built into every Gordon Frame kit piece...ahaha Sorry...could'nt help myself.

This Carpy kit is cool though!.....good ol' Carpy. I often thought of offering a quasi-frame kit...with the gordon "triangulation tabs" and the sliding Tubes "a la APE style".... giving you a more rigid frame kit with no welding requirements... just a hacksaw and a drill! You would really only need the two tabs....4 tubes and hardware....using the oem section just as the Gordon kit....I'm sure it could be done at a bargin!

All good stuff.
Cheers!
B

eurban · « **Reply #35 on:** June 22, 2010, 05:13:18 AM »

Quote from: MCRider on June 21, 2010, 07:36:10 PM

The practical matter is simply...10s of thousands CB750s have the rails cut out with no harmful effects. Another 10s of thousands have replaceable frame rail kits. I think they simply make us feel better. Nothing wrong with that.

Uh, I don't think I would come close to concluding that there are no harmful effects from cutting the rails. Handling performance is a very subjective matter and while catastrophic failure may not be the result, I would bet that there are perceptible and measureable negative effects. Also consider the added grip of modern tires, and today's prevalence of braking and engine performance upgrades.

bikerbart · « **Reply #36 on:** June 22, 2010, 07:06:02 AM »

he charged 85.I asked why on his site says 65,he said error.Kinda shady if you ask me.wouldnt modern upgrades help ease the stress on the frame such as roller bearings,progressive springs,etc.?As I said before,I treat it like its a 37 yr old bike.If I want to carve canyons I would get a modern bike.I am not going to do track days or tour across the country fully loaded,(even though last year I did a 2500 mile trip.)I am not a big person,156,If I dont like it I can always weld it,right?I have always had older bikes because they are cheap and usually run(At Least the japanese ones do)One day after I pay off my student loans that is when I will buy another modern bike.(newest one I had was my 89 hawk gt650)

nippon · « **Reply #37 on:** June 22, 2010, 09:06:06 AM »

Probably my problem, I'm not interested in riding bikes w/o a SOHC engine.
If you have a rolling chassis (w/o engine) of the CB750,.....just push with your foot against the frame to the inside direction at the footpeg location.
The frame will twist recognizeable almost 15 mm at this location. I think, with the installed kit, it does not get better.
@bikerbart,.....if everbody would think this way, there was never be a need for developing tapered beerings, better rear shocks, better tires or any other parts which improve the handling of the SOHC.
Everybody would have to use a modern bike and aftermarket parts would not exist.
Anyway, if you are happy with a conversion kit, use it.

nippon

754 · « **Reply #38 on:** June 22, 2010, 09:15:28 AM »

Cut frames are pretty handy for changing cams, fixing headgaskets, swapping heads..re-ringing in mid season..

I for one would not like to have to pull a motor in a campground 1500 miles from home, just to fix a blown head gasket..

MCRider · « **Reply #39 on:** June 22, 2010, 01:09:10 PM »

Nippon, Terry, et al: Points taken. The kit is handy for dragsters doing top end work at the track. Glad i had it to do a cam swap 1500 miles from home. Plenty fine (IMO) for street use.

Full out road race well probably not. I had mine while I was roadracing, but I was never any good on it (got some trophies on my buddies 750F though.).

I'll take my project to a track day when its finished and report back. If I don't crash it, its a success?

aberle · « **Reply #40 on:** April 17, 2011, 05:23:43 PM »

i just got this kit any updates on how its been working for you?

bikerbart · « **Reply #41 on:** April 17, 2011, 07:17:44 PM »

well,when it runs,its fine.I dont beat on it so I hardly notice a difference.

Don R · « **Reply #42 on:** April 17, 2011, 09:26:12 PM »

My 1970 bike was already cut, I used a Gordons kit and the tubes removed from a donor frame. It had been wrecked and needed a bit of straightening. Just for giggles I counter-bored part way through the kit ends just for a little lightening. I probably would not have felt the difference though. Mine has an 836, rode OK before but I'm not a corner carver.

bikerbart · « **Reply #43 on:** August 14, 2012, 10:23:47 AM »

I have had interest lately in the Kit,so here is a pic of how I mounted it

CB750F2 · « **Reply #44 on:** August 14, 2012, 03:15:08 PM »

Bikerbart, what is the wall thickness of the kit tubes - is it the same as the bike tube thickness? Is there any reason why the frame that is cut away could not be re-used? If it could be re-used then all that needs to be manufactured are the four sleeves. Also the centre gusset could be rejoined ah la Gorden's kit. Another idea would be to machine up some plugs - 8 of - that could be weldedinside the tube ends. This would allow the coupling bolts to be drilled and tapped. Pat

bikerbart · « **Reply #45 on:** August 14, 2012, 04:06:03 PM »

It is a lot thicker than the original,and you are correct in thinking just use the original frame and make some sleeves,this is an older pic so I dont really know the actual thickness,but it is stout.

lucky · « **Reply #46 on:** August 14, 2012, 04:22:23 PM »

Quote from: axehole54 on June 21, 2010, 06:34:16 PM

I was lucky enough to have bought a 78k with the tubes cut and everything siliconed all to hell going to build something myself to repair the frame similar to Carpy's system... but honda probably should have done something back then to make the head accessible

People back then were not as lazy as they are now.

The CB750's ran for years and years without hardly any work needed, unlike other motorcycles of the era.

Killer Canary · « **Reply #47 on:** August 14, 2012, 07:54:25 PM »

Don't buy a frame kit, buy a 550!

shinyribs · « **Reply #48 on:** August 14, 2012, 09:59:46 PM »

Quote from: Ricky_Racer on June 21, 2010, 07:13:33 PM

I have Gordon's kit because I like the fact that it's nicely machined, welded in place and can be adjusted to provide some stress.

But the pictured kit in this thread begs the question: Why bother?

IF this solution is just as good, it would seem that you could take four pieces of tubing with the correct ID to just slip over the side rails , add two more pieces of 1/2" wide plate a couple inches long to support the short braces tieing the side rails to the backbone, figure 12 bolts and self-locking nuts and Badda-Bing, cut your old side rails and braces, slip over the four new short tubes, drill and bolt everything, and be done with it. Opinions?

Ha! Anybody want a kit for $29.95? Looks doable to me! RR

LOL That's what I did. I reused the factory piece I cut out just so I WAS able to tie back in to the back bone as. I figured it would be stronger that way. Of course,after I cut the frame out I realized I needed something from the store...so I slapped the tank back on and rode without ANY of it in place. It actually did just fine with anything,but in the long run,I'd rather have something in there

NOTE: I did NOT attach it with hose clamps! LOL. That was just to hold it all in place while I drilled the holes so it would all line up later

PART_1335715945836 by Shiny Ribs, on Flickr

Don R · « **Reply #49 on:** August 14, 2012, 11:37:04 PM »

T bolt hose clamps hold the front motor plate of the 567 big block in my dragster. 60 feet in 1.09 sec. hasn't fallen out yet. Lol.

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Author Topic: carpy's frame kit (Read 10795 times)

Swoop